It is known that a internal combustion engine with the exhaust gas recirculation means, which intakes a part of the exhaust gas with the fresh air so as to lower the combustion temperature of the engine for reducing NOx (Nitrogen Oxides) in the exhaust gas. This type of internal combustion engine has a recirculation valve in the exhaust gas recirculation pipe, through which the exhaust gas returns to an intake pipe of the engine. This recirculation valve adjusts the recirculation rate of the exhaust gas in the intake gas.
The recirculation quantity of the exhaust gas is adjusted according to the driving condition of the internal combustion engine. That is, the opening degree of the recirculation valve is increased or decreased based on the commanded fuel injection value and the rotational frequency of the engine.
Further, the opening degree of the recirculation valve is decreased quickly to the minimum when the increase in a unit time of the commanded fuel injection value exceeds a given value. The increase of the fuel injection value is interpreted as a request to enlarge the torque, to prevent the smoke exhaustion by the air shortage caused especially by the response delay of the supercharger.
The commanded fuel injection value is ordinary adjusted by the acceleration opening operated by the driver. However, in these days, the fuel injection value is also adjusted by the cruise controller, which controls the driving state to a given regular state, for example, the driving speed to a fixed value, as shown in the Japanese Patent No. 3316867. The cruise control is adopted for the constant traffic flow in an exclusive motorway.
Here the cruise controller controls the fuel injection value according to the feedback of the variation of the inclination of the road surface, which may shorten the life of the recirculation valve, when it moves frequently in some condition of road surface.